UV embossing is a technology of disposing UV curing material between a mold and substrate, pressing the material into the undulating mold structure under pressure, and copying the mold via stripping after UV curing. Embossing and more specifically, nano-embossing plays an irreplaceable role in graphical production (e.g. optical film, anti-counterfeit labels, CD, MEMS and etc.). It is an important researching object in optical display, information storage, biological medicine and other high-tech fields. Compared to other micro-nano processing means (e.g. UV lithography, electron beam and ion beam lithography), nano-embossing has the advantages of simple operation, high resolution, and good repetition.
At present, technology of single-side embossing on a surface of substrate has been very mature. Patterns with less than 100 nm line width may be produced via single-side embossing apparatus with a flat or curved surface mold. But in some areas such as double anti-counterfeiting label, single-side embossing technology can no longer meet the requirements. In these areas, double-side embossing technology mainly comprises the following two types:
One is double-side embossing technology with 2 rollers, which is based on the principle of single-side embossing with a curved surface mold, wherein two coated curved surface mold or directly carved pattern rollers are disposed on an apparatus, for embossing on a positive and negative side respectively. The method can implement rapidly roll to roll double-side embossing. However, the alignment accuracy of the pattern on the positive and negative side in each embossing unit is one of the important factors of the embossing quality. Double-roller technology uses two rollers with the same diameter in theory, for the double-side alignment. But in fact, there is some error in the production of nip rollers, the diameter cannot be completely consistent, slight differences will be significantly enlarged after thousands of embossing, therefore the embossing pattern on the positive and negative side cannot be in counterpoint. In addition, the mold is coated on the nip roller, which will easily introduce angle error, lead to pattern rotation on one side, and lose double side counterpoint.
The other is double-side embossing technology with two flat molds, usually disposing two un-deforming flat molds on the positive and negative side of substrate, wherein the substrate is coated with embossing material on the positive and negative side, two molds and the substrate is closely attached and finish double-side embossing of a unit in vacuum. Although this method can implement the patterns alignment on the positive and negative side, but it requires the introduction of vacuum steps to remove air bubbles between the mold and the embossing material, and comprises two problems: (1) a confined space is needed to create a vacuum environment, (2) Vacuum pumping process will take long hours. These problems decide the method cannot implement rapidly roll-to-roll producing.